1. Field of the Invention
The present invention relates to the fields of pixel driving technology of the light emitting diode display, and in particular to a pixel driving circuit and an array substrate of organic light emitting diode (OLED) display and the corresponding display.
2. The Related Arts
Organic Light Emitting Diode (OLED) has features of faster response, higher contrast, wider viewing angle and etc. compared to conventional liquid crystal panel. Hence, OLED has the increasingly widespread attention from the display technology developers.
FIG. 1 shows the schematic diagram of a pixel driving circuit of OLED display according to the existing technology. It is a pixel driving circuit of voltage driving type composed by 2 TFT transistors and a capacitor (2T1C).
Wherein, under the control of the signal of the scanning control line (Gate_n), a first transistor TFT1 will transfer the voltage from the data lines (Data_n) to the gate of the driving transistor TTFT2, the driving transistor TFT2 will transform the data voltage into the corresponding current for the OLED. During normal operation, the driving transistor TFT2 should be in the saturation region to provide a stable driving current for OLED within the scanning time of one row.
Referring to FIG. 2, it shows a gate scanning timing diagram of the circuit used in FIG. 1. Wherein, CLKA/B is a clock signal of the gate scanning IC, and STV is a gate scanning synchronizing signal. Wherein, the gate scanning is achieved by turning on row by row. After the previous row scanning is turned off, the next row scanning is turned on. The scanning time is 1/(F×n). Wherein, F represents the field scanning frequency of the OLED display, and n represents the row scanning frequency of the OLED display.
However, in the existing pixel driving circuit, when inputting the same gray scale voltage, there are different threshold voltages within different driving transistors TFT2 corresponding to different pixel units, so different driving transistors TFT2 will generate different currents, leading to inconsistency of driving current in a OLED display panel. Moreover, for high-resolution AMOLED display, it is limited by the size of the TFT1, and each row of pixel units begin to work just after the previous row scanning time is finished, so the saturation current of the TFT1 can not be satisfied. That is, in the scanning time of one row, there may be a risk that the storage capacitor C1 can not be charged to the predetermined voltage, which will affect the driving current input to the OLED.